1. Field of the Invention
The present invention relates to an image sensor device, more particularly to an image sensor device of fully contact type which is installed in an image input device such as a facsimile or a hand-held scanner.
2. Description of the Related Art
As an image sensor device, there have heretofore been image sensors of the fully contact type which are installed in a small sized image input device such as a facsimile or a hand-held scanner, and various structures of image input devices have been known. Among these image sensors, a thin film light source of plane radiation type has been used as means for further achieving a reduction in a size of the image sensor devices. For the image sensor device using such thin film light source, various structures have been known. Such a typical image sensor device will be described below.
Japanese Patent No. Showa 59-41629 discloses a first conventional example in which an image sensor is used. FIG. 1 is a perspective view showing a configuration of an image sensor device of the first conventional example.
The image sensor device consists of an optical fiber collection member 1201 composed of a plurality of bundled optical fibers 1202; an illumination unit 1204 utilizing electroluminescence (EL); photoelectric conversion elements 1203 utilizing a thin film semiconductor such as amorphous silicon (a-Si); and a light blocking unit 1205. In FIG. 1, although only three photoelectric conversion elements 1203 are shown, actually the photoelectric conversion elements 1203 of such structures are sequentially arranged in a arrangement direction. The number of the photoelectric conversion elements ranges from several hundreds to several thousands.
Next, an operation of the image sensor device will be described. Light emitted uniformly from the illumination unit 1204 travels through the optical fibers 1202 to reach a document 1290. The reflected light from the document 1290 partially travels through the inside of the document and a small gap between the document and the optical fiber collection member 1201, and passes through the inside of the optical fiber 1202. This reflected light is detected by the photoelectric conversion element 1203. Brightness information for one line of the document can be obtained from an output from the plurality of photoelectric conversion elements arranged on a line. By recording the information while continually moving the document in parallel, reading out for the document is conducted. If the light from the illumination unit 1204 is incident on the photoelectric conversion 1203, contrast of the image read out from the document is deteriorated. This is prevented by the light blocking unit 1205 which prevents light from being directly incident on the photoelectric conversion element 1203. Moreover, the optical fiber collection member 1201 also functions as a supporter for the photoelectric conversion element 1204 formed by thin film processes.
Japanese Patent Laid Open No. Heisei 7-58910 discloses a second conventional example in which an image sensor such as a CCD and a MOS type sensor, formed of crystalline silicon, is used. FIG. 2 is a section view showing a configuration of an image sensor device of the second conventional example.
This image sensor device is constructed such, that on a supporting body in which optical fiber array 1301 is sandwiched between opaque glass substrate 1302 and transparent glass substrate 1303, an image sensor chip 1305 such a CCD is mounted interposed by adhesion layer 1309 in such a way that light receiving element array 1306 faces the document. At this time, the image sensor chip 1305 is electrically coupled to an external circuit (not shown) by a circuit conductive layer 1308, formed on the opaque glass substrate 1302, and an electrode 1307. Moreover, an illumination unit 1310 utilizing electroluminescence (EL) is arranged, close to the light receiving element array 1306, on an upper portion of the transparent glass plate 1303. A light blocking layer 1304 is provided on the surface of the transparent glass substrate 1303 on the document side.
Next, an operation of the image sensor device of the second conventional example will be described. Light emitted from the illumination unit 1310 passes through the transparent glass plate 1303 to be incident on the side surface of the optical fiber array 1301. The light illuminates the document 1390 located at the place facing the light receiving element array 1306. The reflected light from the document passes through the optical fiber array 1301 so that it is detected by the light receiving element 1306.
The two conventional examples described above use the optical fiber collection member. A conventional example using no optical fiber collection member will be described as a third conventional example. The third conventional example is an image sensor device disclosed in Japanese Patent Application Laid Open No. Showa 62-27975. FIG. 3 is a sectional view showing a configuration of the image sensor device of the third example.
The image sensor device of the third conventional example is constituted such that a sensor section 1410 and an illumination section 1420 are formed in parallel on a glass substrate 1401, both being close to each other. The sensor section 1410 is constituted by arranging an a-Si layer 1403 between a bottom electrode 1402 and a transparent electrode 1404 and the illumination section 1420 is constituted by arranging an EL element 1406 formed of a thin film between an electrode 1405 and a transparent electrode 1407.
Next, an operation of the image sensor device of the third conventional example will be described. Light emitted from the illumination section 1420 toward a document 1490 passes through a protection layer 1408 to irradiate the document 1490. The reflected light from the document 1490 is partially detected by the sensor section 1410, thereby obtaining brightness information of the document 1490.
The conventional examples explained above have the constitution that the illumination section and the sensor section are arranged close to each other on the same plane. A conventional example in which both illumination and sensor sections are stacked will be shown as a fourth conventional example. The fourth conventional example is an image sensor device disclosed in Japanese Patent Application No. Heisei 5-344280. FIG. 4 is a sectional view showing the constitution of the image sensor device of the fourth conventional example.
The image sensor device of the fourth conventional example is constituted by stacking a transparent substrate 1501 having a light receiving element array 1502 formed therein and a transparent substrate 1503 having a dispersion-type EL element 1504 formed therein interposed by an adhesive layer 1511, the dispersion-type EL element 1504 being composed of a transparent electrode 1505, a light emission layer 1506, an insulation layer 1507 and an opaque electrode 1508. In the dispersion-type EL element 1504, a light transmission window 1510 is formed corresponding to the light receiving element array 1502. Since the light from the dispersion-type EL element 1504 should not be directly incident on the light receiving element array 1502, a light emission section is covered with a frame portion 1509 and the opaque electrode 1508.
Next, an operation of the image sensor device of the fourth conventional example will be described. The light emitted from the light emission layer 1506 passes through the transparent substrate 1503 to illuminate a document 1590. The reflected light from the document 1590 partially passes through the light transmission window 1510. The light having passed through the light transmission window 1510 is detected by the light receiving element array 1502, whereby information as to brightness of the document can be obtained.
By combining the conventional components of the conventional examples described above, specifically, according to usage of either the dispersion-type EL element or the thin film EL element for the light source, usage of either the sensor formed of crystalline silicon such as CCD or the sensor formed of a thin film semiconductor such as the a-Si for the image sensor, and formation by either parallel arrangement of the light source section and the sensor section or stacking of them, many types of constitutions by combination can be available.
With progress of development of an organic EL light source, the organic EL light source possesses more advantageous features for being mounted on the image sensor device because it is formed to be thinner, has higher brightness and capable of being driven by lower voltage than the dispersion-type EL light source. FIG. 5 is a exploded perspective view showing an example of the image sensor device inferred from the above described conventional examples.
The image sensor device of FIG. 5 is constituted by combining an image sensor 1610 and a thin film light source 1620, the image sensor 1610 having the structure in which a plurality of photoelectric conversion elements 1612 are uniformly arranged on an image sensor substrate 1611 and the thin film light source 1620 having the structure in which a transparent electrode 1622 is formed on a transparent substrate 1621, a light emission layer 1623 is formed on the transparent electrode 1622, and an opaque electrode 1624 having a plurality of opening portions 1625 formed corresponding to the photoelectric conversion elements 1612 is formed on the transparent substrate 1621.
FIG. 6A and FIG. 6B are drawings for explaining the image sensor device in detail. FIG. 6A is a sectional view of a plane including the opening portion 1625 and the transparent electrode 1622, and FIG. 6B is a bottom view when the thin film light source 1620 and the image sensor 1610 are viewed from the document. As is shown in FIG. 6A, the light emission layer 1623 and the photoelectric conversion element 1612 are arranged in parallel in close proximity and stacked with adhesive layer 1630 interposed between them. Moreover, as is shown in FIG. 6B, the light incident on the surface of the image sensor 1610 facing the thin film light source 1620 is shaded by the opaque electrode 1624 except for the center portion of the photoelectric conversion element 1612. Here, although for simplicity of explanation the light emission layer 1623 formed of the organic EL element was described as a conventional component of the thin film light source 1620, a device structure which is constituted by stacking more than two kinds of organic thin films has been known as the light emission layer, as is commented in literature, for example, xe2x80x9corganic light emission devicexe2x80x9d, O Plus E, March 1996, pp. 70-75. These devices possess sufficient light emission intensity to be mounted on the image sensor.
Next, an operation of this example will be described. Light emitted from the light emission layer 1623 passes through the transparent substrate 1621 to illuminate a document 1690. The reflected light from the document 1690 partially passes through the transparent substrate 1621 and the opening portion 1625 and is detected by the photoelectric conversion element 1612, whereby information as to brightness of the document can be obtained.
In the conventional image sensor device using the thin film light source, it is difficult to input an image thereinto with a high resolution. Moreover, since a power consumption of the light source can not be decreased, it is difficult to install the image sensor device into a portable equipment. The reason for this will be described below.
In general, the thin film light source of surface light emission type possesses the directivity that it radiates light with the maximum intensity toward the vertical direction and radiates light with lower intensity as an angle with respect to the vertical direction increases. Therefore, the portion in the document facing the light emission section of the thin film light source is illuminated most strongly, and the periphery of that portion is illuminated with lower intensity. Moreover, since the reflected light from the document is in general diffused light, the light is reflected toward various directions. Among the light reflected, only the light reflected toward the photoelectric conversion element is alone detected. Therefore, the closer the portion of the document is to the photoelectric conversion element, the higher the probability of the reflected light being incident on the photoelectric conversion element.
Therefore, in the conventional example using no optical fiber collection member, an output from the photoelectric conversion element will reflects brightness information for a portion of the document, such as from the portion facing the illumination section to the periphery around that portion, and the portion facing the photoelectric conversion element to the periphery around that portion. With such circumstances it is impossible to input an image with a high resolution.
In the conventional examples of FIGS. 1 and 2 using the optical fiber collection member, the reflected light from the portion other than that of the document facing the photoelectric conversion element is excluded. Specifically, the reflected light from the place facing the illumination section capable of performing illumination with most effectiveness can not be utilized. Moreover, also in the conventional example using no optical fiber collection member, the light emitted from the thin film light source is reflected by the document so that the proportion of the light incident on the photoelectric conversion element is small. Specifically, a large majority of emitted light is wasted. Since a signal of sufficient quantity can not be obtained under such circumstances, measures to increase the quantity of light emission from the light source such as an enlargement of an area of the light emission section or an increase in a voltage to be applied to the EL element are taken. Since such actions result in increasing the power consumption of the light source, it is not compatible with the aim to manufacture a small sized image sensor device nor for installing an image sensor device into a portable equipment. Moreover, if the area of the light emission section is widened, the resolution of the device is deteriorated from the foregoing reasons.
As described above, the image sensor device utilizing the conventional thin film light source has no ability to input the image with a high resolution. Furthermore, since the utilization efficiency of the light is low, the power consumption of the light source can not be reduced.
In order to improve the image quality of the image sensor device and the utilization efficiency of light, only the portion of the document to be read should be illuminated and the light reflected from other portion should as far as possible be excluded.
The object of the present invention is to eliminate the drawbacks of the prior art by providing an image sensor device which is capable of reading out a document with a high resolution, reducing a power consumption of a light source and capable of being advantageously installed into portable equipment.
An image sensor device of the present invention, which optically reads out a document, comprises an image sensor portion having a plurality of light receiving elements arranged regularly, each of which faces a document to be read out; and a thin film light source arranged tightly contacted on the document side of the image sensor portion, the thin film light source emitting light toward the document. The thin film light source has more than one light emission portion corresponding to each of the light receiving elements, the light emission portion having an area smaller than that of the light receiving element, and the light emission portion has a light blocking layer on the light receiving element side, and is arranged on a lower surface of the light receiving element between the light receiving element and the document.
Furthermore, the thin film light source may comprise light emission portion having an area larger than that of the light receiving element corresponding to each of the light receiving elements, the light emission portion may have light blocking layers on the light receiving element side, and the light blocking layer may have more than one opening portion for transmitting the light from the document to the light receiving element.
Furthermore, in order to irradiate the light emitted from the thin film light source onto only a specific portion of the document, a light absorption unit may be disposed at a portion other than the document irradiation portion between the light emission portion and the document. A reflection mirror and a dielectric mirror may be integrally formed as a conventional component of the thin film light source, which are interposed by the light emission portion of the thin film light source. An optical fiber collection member for converting the light to parallel light may be disposed between the light emission portion and the document.
Moreover, an optical fiber collection member (for converting the light to parallel light) may be disposed between the light emission portion and the document and optical means for bending the course of the light to the predetermined direction may be disposed between the optical fiber collection member and the document. This optical means should be any of a diffraction grating, a micro lens and a V-shaped groove.
Moreover, a light guiding means may be provided for guiding the light emitted by the thin film light source to either one light receiving element or to specified light receiving elements among the plurality of light receiving elements, as well as adjusting means for adjusting the sensitivity of the image sensor section depending on a signal output detected by the specified light receiving element. The light guiding means may be a light reflection layer disposed between the thin film light source and the document.
The light emission portion of the thin film light source may be composed of a transparent electrode an opaque electrode and an organic thin film held between the transparent and opaque electrode, and the opaque electrode may be formed of a material functioning as a light blocking layer for the region except for the light receiving element of-the image sensor portion. Light blocking means may be disposed at a region other than the light receiving element of the image sensor portion. The image sensor portion may be either an image sensor formed on a silicon wafer or an image sensor formed on the transparent substrate by thin film semiconductor processes. The thin film light source may emit lights of a plurality of different colors, and an optical fiber collection member may be provided between the thin film light source and the document.
The light emission section of the thin film light source having an area smaller than that of the light receiving element is disposed on the lower surface of the light receiving element, and the opening portion is disposed at the light emission section having an area larger than that of the light receiving element provided on the lower surface of the light receiving element, whereby the light which is incident onto the narrow portion of the document at the lower portion of the light emission portion is reflected to be incident onto the light receiving element right above the document, resolution of the light receiving element is increased, and the power consumption of the light source can be reduced.
By absorbing light for other than the necessary portion by the light absorption unit, by changing the light beam to a parallel light by the reflection mirror and the dielectric mirror which are integrated together, by changing the light beam to a parallel beam by the optical fiber collection member, and by bending the course of the light beam, which is made parallel by the optical fiber, by optical means the light is concentrated to the predetermined place corresponding to the light receiving element. Thus, the reflected light from a small area is incident onto the light receiving element, thereby increasing resolution of the light receiving element.
The light emitted from the light source is guided to the specified light receiving element by the light guiding means, and the sensitivity of the image sensor is adjusted depending on the signal output detected, whereby the image sensor performs a stable operation.
By preparing the opaque electrode contacting the organic thin film from a material possessing light blocking property, it will be unnecessary to provide a separate light blocking layer.
By combining light sources emitting different colors, color image input with a high sensitivity can be realized with out a color filter.
By arranging the optical fiber collection member between the thin film light source and the document, a function as a supporter for the image sensor can be obtained, as well as a function to protect other structural members.
The above and other object, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate an example of a preferred embodiment of the present invention.